Pneumatic fastener device



May 4, 1965 D. voLKMANN PNEUMATICI FASTENER DEVICE Filed March 6, 1962 INI/ENIGE;

. Ves/mann AT1-o '1111395 United States Patent O M 3,181,428 PNEUMATC FASENER DEVCE Dieter Volkmann, Neustadt am Rnbenberge, Germany, assigner to Bahama G.m.b.H., Hannover, Germany Filed Mar. 6, 1962, Ser. No. 177,915 6 Claims. (Cl. 9l-392) This invention resides in the provision of a pneumatic fastener device to actuate, by pneumatic force, a piston on a Work performing stroke.

A primary object of the invention is to provide a portable device adapted to be connected to a supply of cornpressed air and which will, on the actuation of the trigger or" the device, cause fastener means, such as wire staples, nails, pins and the like, to be driven into a Work piece from a magazine contained in the device.

More specifically, an object of the invention is to provide a pneumatic device for driving fasteners into a Work piece in rapid succession and with high striking power.

Another object of the invention is to provide a portable fastener device actuated by compressed air in that the compressed air causes lthe Working stroke of the piston as Well as its return movement into the initial or starting position, and for the latter movement is required in minimum quantity only.

Another basic object of the invention is lto provide a pneumatic fastener device in such manner that the compressed air not 4only drives the piston with its staple into the work piece, -but also returns the piston into its initial position so that it is not any more necessary for the device to have a return spring for the piston.

Another object of the invention is to provide an eX- tremely simple and eective mechanism for the operation of the fastener device, said mechanism comprising a minimum of elements of novel design and arrangement, suitable for economic manufacture and avoiding any excessive wear.

The pneumatic mechanism of the present invention is designed to drive staples into a Work piece. It is obvious the mechanism may be designed for the use of staples of a ditferent type, the Word staple being used, in this case, in a general sense to cover all fastening means to be driven into a Work piece. The pneumatic device comprises a piston which, when the trigger of the control valve is actuated, is pneumatically driven from its retired initial position to perform .a driving stroke. In the case of constmctions known in the art, the control valve is in communication with the cylinder of the device through a duct. When the control valve is opened, the aerodynamic resistance of said duct which is :to be overcome by the cornpressed air flow prevents instantaneous iilling up of the cylinder to the full compressed air pressure, Due to this delay, the working piston, in its initial posit-ion, cannot receive immediate full acceleration and therefore does not at once reach its full Working performance. This is of particular disadvantage because the driving of staples into Work pieces regularly requires the piston to have strong and instantaneous acceleration in order Vthat the staples are properly driven into the work piece. It is apparent that the device cannot work in a reliable way as long as the delayed acceleration, caused by the flow resistance in the duct, which connects valve and cylinder, is not abolished.

According to the invention, an immediate driving force of maximum amplitude imparted instantaneously is obtained by providing for the cylinder at the end corresponding to the retired initial position of the piston to communicate permanently, with the supply of compressed air and at its opposite end to be connected with the control valve which is opened for the driving stroke of the piston 'and to allow the lair in the cylinder beneath the piston 3,ldl,428 Patented May d, i965 to be freely expelled as the piston proceeds on its driving stroke.

The piston at its one front end, is permanently submitted to the pressure of the compressed air. As soon as the control valve is actuated and the lower part of the cylinder, beneath the piston, communicates with the open air, compressed air may act on the piston with its full pressure, thus moving it instantaneously in the direction of the driving stroke. This causes a high velocity as Well as a high kinetic energy to be imparted to .the piston, thus providing for a high striking power without any need for a large mass of the piston. The amplitude of the driving stroke may be reduced, thus to allow of a rapid succession of operations and a satisfactorily driving of the fasteners.

After the completion of the driving stroke, the control valve, now returned to its initial position, admits air to the bottom of the cylinder beneath the piston so as to return the piston and its driver to their initial positions.

According to another important object and salient feature of the invention, the arrangement of the device is such that the lower face of the piston submitted to the action of compressed air in the course of the return stroke f the piston, has a larger diameter than the upper face permanently submitted to the action of compressed air. lt will be found effective to impart, to the piston, the design of a differential piston the auxiliary piston of which is submitted to the action of compressed air in the course of the return stroke and has a larger face than the main piston permanently submitted to the pressure of compressed air.

According to a further object of the invention, the piston is designed in such a way that its face permanently submitted to the action of compressed air is increased when the piston performs its driving stroke and is reduced again when .the :piston reaches its retired initial position. For this purpose, the piston may be made to pass a socket provided in the cylinder and to fit against an annular surface of said socket when returning to its initial position. As soon as the piston is lifted from said socket at the beginning of its Working stroke, compressed air will act, in addition, on this annular surface whereby the Working face of the piston is then increased.

The above and other objects and lfeatures of this invention will appear from the following detailed description of ltwo preferential embodiments thereof, illustrated in the accompanying drawings, it being understood that the present description is merely chosen by -Way of an example.

In the accompanying drawings,

FiG. 1 is a view, partly in longitudinal section, of a fastener driving device embodying the present invention, and

FIG. 2 is a view, partly in longitudinal section, of a modification of the invention.

Referring now to FIG. 1, the manually portable pneumatic device conssits of a housing body l shaped as a handle .and provided with a suitable iitting 2 for its connection with a supply of compressed air. The housing body l encloses an air chamber 3 which communicates through a duct 4 and a series of ports 5, with a cylinder 6 forming a part of the housing body ll. Reciprocable Within the cylinder 6 is a piston member 7 which is shaped as a differential piston. The upper Working piston S of piston member has a lesser diameter than the lower auxiliary piston 9. The Working piston 8 is slidable in a sleeve l() enclosed by the cylinder 6 and having the same axial length than the working stroke of' piston member 7. The auxiliary piston 9 is guided immediately within the bore id of cylinder 6. At the lower end of piston member is secured a driver ii. A drive track l2 is provided in a nose structure at the lower part of body 1 and communicates with a magazine 13. The driver 11 isV guided in the drive track 12. Gn each working stroke of piston member 7 a staple from the magazine 13 is engaged by driver 11 and through drive track 12 is driven into a work piece.

A There is a duct 14 leading from the bottom of cylinder 6 to a control valve 15 provided in the housing body 1. Said valve is actuated by a trigger lever 16 pivoted in the housing body 1 and communicates with the air chamber 3 as well as with an exhaust duct 17 provided in the housing body 1 and communicating with the atmosphere. Y

On the bottom of lcylinder 6 is mounted an elastic disc 19 serving as a resilient bumper to absorb the impact of the auxiliary piston 9. The lower end of piston member 7 is shaped as a rod and is sealed in relation to the housing body 1 by a sealing ring 20.

In the initial or starting position of the fastener device as illustrated in FIG. l, the control valve 15 connects duct 14 with air chamber 3 and closes it against exhaust duct 17. Compressed air in the chamber 3 flows, through duct 4 and ports 5, to the upper end of cylinder 6, thus acting upon the upper face of working piston 8. Apart lfrom this, said air ows, from air chamber 3, through duct 14, into space 18 of cylinder 6 below the auxiliary piston 9. As the annular lower face of said auxiliary piston 9 is larger than the upper front face of the working piston 8, piston member 7 is maintained in its upper or initial position by compressed air.

When a staple from magazine 13 is to be driven through drive track 12 into the work piece, the operator manually squeezes the trigger lever 16 of control valve 15 whereby the duct 14 is closed against the air chamber l3 and connected with the exhaust duct 17. This causes the air from space 13 beneath the auxiliary piston 9 to exhaust so that no pressure remains in space 18. The compressed air, acting only against the upper face of working piston 8 immediately actuates the driving stroke of piston member 7 so that a staple is driven, with great force, by driver 11 into the work piece. As the cornpressed air permanently acts against main piston 8 a high velocity quick movement of piston member 7 will be effected when the control valve 15 is actuated. The driver 11 receives a large kinetic energy and performs its working stroke with great speed and, with a powerful blow, drives the staple into the work piece.

After the completion of the driving stroke, the operator releases trigger lever 16 causing the pressure of compressed air in air chamber 3 to return valve 15 in its lower or initial position in which duct 14 is closed against exhaust duct 17 and connected with air chamber 3. Now compressed air acts upon the lower face of auxiliary piston 9. As this face is larger than the upper front face of main piston 8, piston member 7 is forced upwardly and restored to its initial or inoperative position.

In the modification of the invention illustrated in FlG. 2, the housing body 2.1 of the device encloses an air chamber 23 which is provided with a fitting 22 for the admission of compressed air. The air chamber 23 is in permanent and open communication, by means of a duct 24 and a series of ports 25, with the upper part of a cylinder 26. The cylinder 26 consists in a sleeve inserted in a bore of the front part of the housing body Z1. A piston 27 is reciprocable in the cylinder 26 and is provided, at its upper end, with a hollow cylindrical extension 23 enclosing a rod 29 secured to the piston 27 by means of a disc 30. The hollow cylindrical extension 2S of the piston 27 is guided in a socket or jacket 31 secured to the housing body 21 and is sealed against socket 31 by a sealing ring 32. The upper face of piston 27 is provided with a recess 33 of a larger diameter than `the socket 31 and sealed against the lower end of socket 31 by a sealing disc 34 lodged in the recess 33. A duct 35 in the lower part of the body 21 communicates the cylinder 26 with a control valve 36. YThe trigger lever 37 of the valve 36 is pivoted in the housing body 21. The

d valve 36 communicates through a bore 38 with the air chamber 23. The stem of the valve 36 has a clearance between the housing body 21 forming an exhaust duct 39.

The piston rod 29 is sealed, in the bottom part 40 of cylinder 26, by a sealing ring d1 and connected to the driver 42 which, with each working stroke, drives staple from Vthe magazine d3, through the drive track 44, into a work piece. The bottom part itl of cylinder 26 is provided with an elastic annular member so as to absorb the impact of the piston 27 at the end of its working stroke within the space 46 of cylinder 26. The upper end of the cylinder 26 is closed by a cap 47 secured to the housing body 31 and having a vent hole 4S.

In the initial or inoperative position of the parts as shown in the drawing control valve 36 connects space 46 beneath piston 27, through the duct 35 and the bore 38, with the air chamber 23 so that the lower face of piston 27 is submitted to the action of compressed air. By means of the ports 25, air permanently flows from air chamber 23 to the upper annular face of piston 27. As the lower face of piston 27 is larger than the upper annular face of piston 27 limited by the inner face of cylinder 26 and the outer face of socket 31 the compressed air in space 46 forces the piston 27 in its initial or inoperative position.

When control valve 36 is actuated by squeezing trigger lever 37, the hole 38 is closed and the duct 35 is connected with the exhaust duct 39 of the valve stem. The air in space 46 of cylinder 26 is exhausted and no pressure is left beneath piston 27. Therefore the air only acting against the upper annular face of piston 27 between cylinder 26 and socket 31 will initiate the driving stroke of piston 27. As soon as piston Z7 is lifted from the lower end of socket 31, the upper working face of piston 27 is increased by the annular face of socket 31 and the compressed air now acts, against the whole upper face of piston 27, thus eecting a corresponding increase of kinetic energy and, consequently, of striking power of piston 27. This will cause the driver 42 united with the piston 27 by the rod 29, to drive the staple at high speed and with great force into the work piece.

After completion of the working stroke, trigger lever 27 is released and valve 36 returns to its initial position in which the duct 35 is closed against the venting duct 39 and, by the hole 38, communicates with the air charnber 23. Now compressed air flows, through the air chamber 23, into the space 46 and acts against the lower face of piston 27. As this face is larger than the upper face of piston 27 permanently submitted to the pressure of the air, piston 27 is returned to its starting position.

In order not to slow the return movement of the piston 27, by the action of the air stored within the cap 47, the latter is provided with the vent hole 43 through which air between cap 47 and socket 31 may exhaust. i Apart from pneumatic fastener devices, percussion equipment of a different nature may likewise profit by the invention and its advantages as the permanent action of the compressed air on the piston results in a high strik- Ving power in spite of small reciprocating masses so that the percussion tool will suifer comparatively little recoil, a feature bound to facilitate its operation to a considerable extent.

It is apparent that the examples shown above have been given solely by way of illustration and not by way of limitation and that they are subject to many variations and modiications within the scope of the present invention. All such variations and modications are to be included within the scope of the present invention.

I claim:

l. A pneumatic fastener inserting device comprising a housing body, a cylinder having an upper and a lower end, a piston reciprocable in said cylinder, a driver xed 'to said piston and actuates thereby to drive a staple, said housing body having an air chamber communicating with a source of compressed air, a permanently open duct between said air chamber and said upper end of the cylinamigas der, and a second duct in said housing body leading to said lower end of the cylinder, a manually operated valve adapted to control the flow of compressed air to said second duct, said housing body further having a vent duct communicating with said valve, whereby when in its normal position said valve is closed said second duct communicates with said air chamber, thus causing cornpressed air also to act upon the lower face of said piston thereby maintaining said piston in a retired initial position, and when said valve is operated said second duct is closed against said air chamber and said second duct communicates through said vent duct to atmosphere thus causing compressed air to act solely upon the upper face of said piston, thereby to bring about an immediate movement of said piston in its staple driving direction, and means increasing during the course of the working stroke the effective area of the upper face of said piston permanently submitted to the action of compressed air, as compared to the size of said upper face in the retired initial position of said piston, a part of said upper face being vented to atmosphere in said retired initial position.

2. A pneumatic fastener inserting device according to claim l, wherein the effective surface area of the upper face of the piston is smaller than that of the opposite face of the piston.

3. A pneumatic fastener inserting device comprising a housing body, a cylinder having an upper and a lower end, a piston reciprocable in said cylinder, a driver fixed to said piston and actuates thereby to drive a staple, said housing body having an air chamber communicating with a source of compressed air, a permanently open duct between said air chamber and said upper end or" the cylinder, and a second duct in said housing body leading to said lower end of the cylinder, a manually operated valve adapted to control the flow of compressed air to said second duct, said housing body further having a vent duct communicating with said valve, whereby when in its normal position said valve is closed, said second duct communicates with said air chamber, thus causing compressed air also to act upon the lower face of said 4G piston thereby maintaining said piston in a retired initial position, and when said valve is operated said second k S duct is closed against said air chamber and said second duct communicates through said vent duct to atmosphere thus causing compressed air to act solely upon the upper face of said piston, thereby to bring about an immediate movement of said piston in its staple driving direction, and a sleeve fixed at the upper end of said cylinder, said sleeve having an annular face bearing in the upper face of said piston in the retired initial position of the piston, whereby the eiective area of the upper face of the piston permanently submitted to the action of compressed air is increased during the course of its Working stroke, said piston having an upper cylindrical extension vented to atmosphere.

4. A pneumatic fastener inserting device according to claim 3, wherein the piston has an annular recess on its upper face adapted to receive the annular face of the sleeve.

5. A pneumatic fastener inserting device according to claim 4, wherein a disc of sealing material is disposed in said recess.

6. A pneumatic fastener inserting device according to claim 5, wherein the diameter of the recess is larger than that of the sleeve to an extent whereby the compressed air may penetrate freely to the bottom of the recess as soon as the piston commences to move in the stapler driving direction.

References Cited by the Examiner UN iTED STATES PATENTS 1,753,499 4/30 Burger l44.4 2,219,739 10/40 Duncan l-44-4 2,983,922 5/61 Iuilfs 1-420 2,989,750 6/61 Mcllvin 1-44.4 X 3,640,709 6/62 Wandel 91-416 3,055,344 9/62 Fisher 1-44.4 X 3,056,964 10/62 Beckman 91-461 3,106,134 10/63 Osborne 91-461 FRED E. ENGELTHALER, Primary Examiner. GRANVILLE Y. CUSTER, JR., Examiner. 

1. A PNEUMATIC FASTENER INSERTING DEVICE COMPRISING A HOUSING BODY, A CYLINDER HAVING AN UPPER AND A LOWER END, A PISTON RECIPROCABLE IN SAID CYLINDER, A DRIVER FIXED TO SAID PISTON AND ACTUATES THEREBY TO DRIVE A STAPLE, SAID HOUSING BODY HAVING AN AIR CHAMBER COMMUNICATING WITH A SOURCE OF COMPRESSED AIR, A PERMANENTLY OPEN DUCT BETWEEN SAID AIR CHAMBER AND SAID UPPER END OF THE CYLINDER, AND A SECOND DUCT IN SAID HOUSING BODY LEADING TO SAID LOWER END OF THE CYLINDER, A MANUALLY OPERATED VALVE ADAPTED TO CONTROL THE FLOW OF COMPRESSED AIR TO SAID SECOND DUCT, SAID HOUSING BODY FURTHER HAVING A VENT DUCT COMMUNICATING WITH SAID VALVE, WHEREBY WHEN IN ITS NORMAL POSITION SAID VALVE IS CLOSED SAID SECOND DUCT COMMUNICATES WITH SAID AIR CHAMBER, THUS CAUSING COMPRESSED AIR ALSO TO ACT UPON THE LOWER FACE OF SAID PISTON THEREBY MAINTAINING SAID PISTON IN A RETIRED INITIAL POSITION, AND WHEN SAID VALVE IS OPERATED SAID SECOND DUCT IS CLOSED AGAINST SAID AIR CHAMBER AND SAID SECOND DUCT COMMUNICATES THROUGH SAID VENT DUCT TO ATMOSPHERE THUS CAUSING COMPRESSED AIR TO ACT SOLELY UPON THE UPPER FACE OF SAID PISTON, THEREBY TO BRING ABOUT AN IMMEDIATE 